On Fri, Mar 05, 2021 at 04:02:16AM -0500, Jeff King wrote:
> I don't know offhand if this trick actually works. I can imagine it
> does, but it hinges on the subtlety between an integer descriptor and
> the underlying "file description" (the term used in POSIX). Does binding
> a socket operate on the former (like close() does not close the parent's
> descriptor) or the latter (like lseek() impacts other descriptors).
>
> I'd guess the latter, but I wasn't sure if you were suggesting this from
> experience or if you just invented the technique. ;)
I was curious, but this does indeed work:
-- >8 --
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <sys/wait.h>
#include <unistd.h>
#include <stdlib.h>
int main(void)
{
int listen_fd, client_fd;
struct addrinfo *ai;
pid_t pid;
getaddrinfo("127.0.0.1", "1234", NULL, &ai);
listen_fd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
pid = fork();
if (!pid) {
bind(listen_fd, ai->ai_addr, ai->ai_addrlen);
return 0;
}
waitpid(pid, NULL, 0);
listen(listen_fd, 5);
client_fd = accept(listen_fd, NULL, NULL);
write(client_fd, "foo\n", 4);
return 0;
}
-- >8 --
-Peff
